Progress 10/01/99 to 09/30/05
Outputs
The initial objective was to assess current and experimental sweet corn cultivars for susceptibility to maize dwarf mosaic virus (MDMV) and to identify local weed hosts for the pathogen. In total, approximately 60 selections were evaluated and yielded a single genotype displaying tolerance to yield reductions. This tolerance was incorporated into at least one commercial hybrid. Efforts to identify alternate hosts were not successful.
Impacts
Results were valuable to commercial sweet corn breeders and ultimately to sweet corn producers in the Hudson Valley. Commercial hybrids were utilized to good effect during the 8-10 year period of widespread infections and served to significantly moderate yield and quality reductions.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
It is commonly believed that corn earworm (CEW) do not oviposit on sweet corn silks after they have dried. To test this perception, we hypothesized that CEW cease to oviposit on silks that are 50 percent dried. Field experiments were performed utilizing silk dryness treatments ranging from 0 to 75 percent and ear cages made of netting to prevent oviposition before the silk dryness targets were attained. Under relatively high infestations during 2001 and 2002, results suggested that oviposition does not cease when silks are 50 percent dry. Under moderately high infestations during 2004, results again suggested that oviposition continues on silks well past 50 percent estimated dryness. It was apparent however, that the results were confounded and cast into doubt by the circumvention of the cages by a small percentage of larvae.
Impacts
Because a small percentage of larvae somehow either bypass or enter through the exclusionary cages, specific conclusions cannot be drawn at this time. Trials will continue during 2005 with altered experimental procedures to insure complete exclusion of larvae on various silk dryness treatments.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
It is commonly believed that corn earworm (CEW) do not oviposit on sweet corn silks after they have dried. To test this perception, we hypothesized that CEW cease to oviposit on silks that are 50% dried. Field experiments were performed utilizing silk dryness treatments ranging from 0% to 75% and methods to prevent oviposition before the silk dryness targets were attained. Under relatively high infestations during 2001 and 2002, results suggested that oviposition does not cease when silks are 50% dry. Under moderately high infestations during 2003, results again suggested that oviposition continues on silks well past 50% estimated dryness.
Impacts
Previous results and results from a 2003 field study to construct a silk dryness threshold, suggested that CEW adults do not discriminate against oviposition on dry sweet corn silks. It is concluded that under high to moderate infestation pressure situations, CEW adults will continue to oviposit on sweet corn ears, even though fresh silks are no longer available. The results suggest that, over a range of infestation conditions, sweet corn ears have to be protected well past the hypothesized 50% target.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
It is commonly believed that corn earworm (CEW) do not oviposit on sweet corn silks after they have dried. To test this perception, we hypothesized that CEW cease to oviposit on silks that are 50 percent dried. Field experiments were performed utilizing silk dryness treatments ranging from 0 to 75 percent and methods to prevent oviposition before the silk dryness targets were attained. Under relatively high infestations during 2001, results suggested that oviposition does not cease when silks are 50 percent dry. Under extremely high infestations during 2002, results suggested that oviposition continues on silks even after they are 75 percent dry.
Impacts
Results from a two-year field study to construct a silk dryness threshold, suggested that CEW adults do not discriminate against oviposition on dry sweet corn silks. It was concluded that under high to moderate infestation pressure situations, CEW adults will continue to oviposit on sweet corn ears, even though fresh silks are no longer available.
Publications
- Straub, R. W. 2002. Relationship of sweet corn silking stage to oviposition by the corn earworm. NYS IPM Pub No. 128. Cornell Coop. Extn. p 96-99.
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Progress 01/01/01 to 12/31/01
Outputs
It is commonly believed that corn earworm (CEW) do not oviposit on sweet corn silks after they have dried. If true, insecticide treatments could logically cease at some predetermined time interval after pollination, because silks commence drying within hours of pollination. We hypothesized that CEW cease to oviposit on silks that are 50% dried. Field experiments were performed utilizing silk dryness treatments ranging from 0% to 75% and methods to prevent oviposition before the silk dryness targets were attained. Under high infestation pressure from CEW, our hypothesis was not proven, for 50% and 75% silk dryness treatments yielded 58.4% and 44.3% infestation of ears, respectively. Visual estimations of silk dryness however, correspond well to simultaneous measurements of % loss of silk wt.
Impacts
Results suggest that CEW adults do not discriminate against oviposition on dry sweet corn silks, at least not to the extent implied by historical data. Future modification of techniques however, may alter the results.
Publications
- Straub, R. W. 2002. Relationship of sweet corn silking stage to oviposition by the corn earworm. NYS IPM Pub #128. Cornell Coop. Extn. (In Press).
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Progress 01/01/00 to 12/31/00
Outputs
Twenty-seven sweet corn entries obtained from the breeding program of a commercial seed company were evaluated for susceptibility to infestation by corn earworm, fall armyworm and European corn borer. Infestation pressure was extreme (78% infested in Candy Corn, the most susceptible entry). Of 12 Bt transgenics evaluated, seven allowed <1% infestation. The majority of damage to transgenics was by fall armyworm, suggesting that the Cry protein incorporated into these selections was minimally effective against this species. In general, nine genetically resistant entries resulting from conventional breeding techniques allowed 46% to 75% infested ears, suggesting that the resistance factor `maysin' was not holding up under the severe infestation pressure conditions. In some instances, genetic resistant entries allowed more damage than susceptible commercial hybrids.
Impacts
Evaluation of Bt transgenic and genetic resistance sweet corn selections showed that the GM hybrids were in general very resistant to attack by worm pests, while genetic resistance was considerably less effective in preventing attack.
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Current management of sweet corn insects is largely accomplished by multiple applications of pyrethroid insecticides. To enable acceptance by commercial sweet corn producers, novel and traditional reduced-risk insecticides need to be compared with conventional materials in large-scale trials. Two sweet corn plantings were utilized to make such comparisons for control of European corn borer (ECB), corn earworm (CEW) and fall armyworm (FAW). Within a planting designed to make evaluations against first brood ECB, the populations were too low to provide meaningful data against this pest. However, corn leaf aphid populations were high and evaluations showed all reduced-risk insecticides to be very weak against this pest when compared to Warrior. Within a later planting designed to evaluate against late-season worm pests, populations of all three species were very high, allowing for a good assessment of treatment effects. In general, the conventional insecticides
(lamdacyhalothrin, permethrin and cyfluthrin) provided excellent control, while the reduced-risk insecticides (soap, emamectin benzoate, tebufenozide, Bt and azidaractin) performed poorly, allowing 21-40% infested ears. The reduced-risk insecticide spinosad however, provided excellent control of all species and is considered to be a very good candidate to substitute for pyrethroids in many sweet corn control programs. Conversely, the other reduced-risk materials show little promise under reasonable application scenarios.
Impacts
(N/A)
Publications
- Straub, R. W. 1998. Insect control on late-season sweet corn with foliar sprays of conventional and reduced-risk insecticides. Arthropod Mgnt. Tests. (In Press)
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Progress 01/01/97 to 12/31/97
Outputs
Because applications of insecticides to corn whorls have not been consistently efficacious against the first brood of European corn borer, we have continued to investigate a degree-day model to schedule treatments for maximum effectiveness. A biofix of first adult emergence is used to relate degree-day requirements to the observed developmental stages of 25, 50 and 75 percent egg hatch on sentinel plants. An early season planting, timed to receive maximum infestations by first brood corn borer, was used to test an updated regression model based on data from three previous seasons. As in 1994-96 trials, a single treatment of permethrin sprayed to whorls at estimated 50 percent egg hatch or 570-610 degree-days, was superior to treatments applied at the estimated 25 percent or 75 percent egg hatch. Results from four seasons suggest that scheduling of insecticide treatments based on degree-day accumulations for estimated 50 percent hatch will provide maximum control with
a single application. During four seasons, 50 percent hatch occurred between 6/22 and 7/2, at which time pheromone trap data showed adult activity to be 90 percent complete; suggesting that the degree-day model is an improvement over systems that use adult occurrence to schedule treatments for first brood European corn borer.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/96 to 12/30/96
Outputs
Because applications of insecticides to corn whorls have not been consistently efficacious against the first brood of European corn borer, we are investigating a degree-day model to schedule treatments for maximum effectiveness. A biofix of first adult emergence was used to relate degree-day requirements to the observed developmental stages of 25, 50 and 75 percent egg hatch on sentinel plants. An early season planting, timed to receive maximum infestations by first brood corn borer, was used to test an updated regression model based on data from two previous seasons. As in 1994 and 1995 trials, a single treatment of permethrin sprayed to whorls at estimated 50 percent egg hatch or 570 degree-days, was superior to treatments applied at the estimated 25 percent or 75 percent egg hatch. Results from three seasons suggest that scheduling of insecticide treatments based on degree-day accumulations for estimated 50 percent hatch may provide maximum control with a single
application. During three seasons, 50 percent hatch occurred between 6/22 and 6/25, at which time pheromone trap data showed adult activity to be 90 percent complete; suggesting that the degree-day model is an improvement over systems that use adult occurrence to schedule treatments.
Impacts
(N/A)
Publications
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Progress 01/01/95 to 12/30/95
Outputs
The European corn borer first brood annually affects all early-season sweet corngrown in Eastern New York. Because applications of insecticides to corn whorls has not been consistently worthwhile, we are investigated a degree-day model to schedule treatments for maximum effectiveness. A biofix of first adult emergence was used to relate degree-day requirements to the observed developmental stages of 25, 50 and 75 percent egg hatch on sentinel plants. An early season planting, timed to receive maximum infestations by first brood corn borer, was used to test a regression model based on the previous season's data. As in 1994 trials, a single treatment of permethrin applied at estimated 50 percent egg hatch or 530 degree-days, was superior to treatments applied at the estimated 25 percent or 75 percent egg hatch. Data from two seasons suggest that scheduling of insecticide treatments based on degree-day accumulations for estimated 50 percent hatch may provide maximum
control with a single application. During both seasons 50 percent hatch occurred between 6/22 and 6/24, at which time pheromone trap data showed adult activity to be 90 percent complete, suggesting that the degree-day model is an improvement over systems that use adult occurrence to schedule treatments.
Impacts
(N/A)
Publications
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Progress 01/01/94 to 12/30/94
Outputs
The European corn borer first brood annually affects all early- season sweet corn grown in Eastern New York. Management techniques could be improved & perhaps the number of insecticide applications decreased, if there was a system for predicting or estimating the temporal relationship of first brood corn borer egg & larval development & the phenology of early sweet corn cultivars. A biofix of first adult emergence was used to establish degree-day requirements for the developmental stages of 25,50 & 75% egg hatch. A regression model was used to time insecticide treatments for optimum control of early-season infestations. Applications at 495 degree-days, or approximately 50% hatch, provided superior control. Additional data relative to larval & pupal development will enhance the model, & will allow for it's use to predict when a given planting is exposed to probable economic infestations. Stewart's bacterial wilt disease, vectored by corn flea beetle, is a sporadically
occurring disease that affects much of the fresh market sweet corn grown in Eastern New York. Results from trapping studies & on-plant counts of beetles suggest that beetles begin activity during mid-April, & approximately 10 percent of the total season's population is present when the earliest planted corn has emerged. The bulk of the seasonal population occurs between 20 May & 1 June, after which numbers remain low but consistent for remainder of season. These results suggest that sweet corn emerging after 1 June is relatively un.
Impacts
(N/A)
Publications
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Progress 01/01/93 to 12/30/93
Outputs
The bacterial wilt susceptibilities of 44 sweet corn cultivars were evaluated in3 separate plantings during 1992. Results showed that 31 percent were susceptible (greater than 15 percent infected) to natural infection by corn flea beetle. Similar plots were planted in 1993 in attempts to verify these results. Because flea beetle populations overwintered poorly, few meaningful comparisons were possible. When results of both years were considered however, it is apparent that a majority of the sweet corn hybrids currently grown in NY have moderate to high degrees of resistance/tolerance to this disease. Just as importantly, seven entries were susceptible in both years: Sensor; Quickie; Market Star; Sequins; Starburst; Stars and Stripes; and the universally susceptible Jubilee. Flea beetles were monitored by yellow sticky-traps to verify results of 1992. Using a combination of flea beetle counts on plants and on yellow traps we learned that corn flea beetles were
present in the field before emergence of the earliest planted swe et corn, beetles are distributed over much of the field very early in the season, and that cropping history does not appear to influence the abundance of flea beetles the following season. This information increases our understanding of beetle occurrence and although we still cannot accurately predict the potential that beetles are infected, it will aid pest managers when making control recommendations.
Impacts
(N/A)
Publications
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Progress 01/01/92 to 12/30/92
Outputs
Forty-three sweet corn genotypes in two plantings, were evaluated for susceptibility to Stewart's bacterial wilt disease (BW) and to late-season infections of maize dwarf mosaic virus disease (MDMV). Genotypes were selected on basis of seedsmen and grower suggestions. Replicated trials were evaluated 30 Jun. BW infections ranged from 0 - 48.7 percent, and the susceptible standard (jubilee) yielded the highest degree of diseased plants. Two numbered hybrids and eight cultivars (Miracle, Phenomenal, Candy Store, Crossword, Silverado, Zenith, Tuxedo and Honey & Frost) yielded average infections less than 2 percent and could be called resistant. Although eight entries yielded infections over 15 percent, the data suggest that many existing genotypes possess a rather high degree of tolerance to BW. This finding is significant because insecticide sprays to control the flea beetle vector are not cost-effective. A late-planting of the same genotypes was evaluated 13 Aug
for incidence of MDMV. Under a high degree of natural infection (range 0.7 34.2 percent), 13 entries exhibited less than 5 percent infection and could be called tolerant. However, 21 entries exhibited infections ranging from 10 - 34 percent, suggesting that most sweet corn hybrids are highly susceptible to MDMV, MDMV is a difficult disease to manage because attempts to control the aphid vectors with insecticides have had no effect on transmission of the virus. No hybrids displayed significant degrees of tolerance to both diseases.
Impacts
(N/A)
Publications
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Progress 01/01/91 to 12/30/91
Outputs
The iucidence of Stewart's wilt disease (vectored by corn flea beetle) was high throughout NY in 1991. The potential to reduce disease effects through vector control was evaluated by aid of a 2x2x2 factorial design (permethrin and carbaryl applications once/wk. and twice/wk., beginning at the seedling and 2-leaf stage). Results showed permethrin to be significantly better than carbaryl; and that twice/wk. applications were necessary only with carbaryl, when the first application began at the 2-leaf stage. In general, weekly applications of permethrin for 3 weeks reduced the incidence of infection 87%, whereas the same schedule with carbaryl reduced incidence only 40%. It is estimated, however, that under severe disease conditions, twice-weekly applications for a one to two week period would be necessary. Fifteen sweet corn hybrids were evaluated for tolerance to Stewart's wilt. Among entries, the proportion showing infection at the mid-whorl stage ranged from 3% to
63%, and marketable ears ranged from 34% to 76%. There was significant correlation (r=-0.934) between symptomology at mid-whorl and marketable yield. Growers are encouraged to utilize tolerant hybrids wherever possible instead of insecticide applications.
Impacts
(N/A)
Publications
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Progress 01/01/90 to 12/30/90
Outputs
Previous studies showed that applications of Cerone growth-regulator shorten sweet corn hybrids and protected against lodging under high wind velocities, but that applications at certain dosage:timing combinations caused ear husks to shorten and yielded unmarketable ears. Trials in 1990 with varying dosage:timing:variety combinations showed similar effects, and it was concluded that Cerone applications should be limited to low dosages (0.125 to 0.25 lb. AI per acre) and not be applied later than 3-inch length of embryonic tassel.
Impacts
(N/A)
Publications
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Progress 01/01/89 to 12/30/89
Outputs
Previous studies showed that applications of Cerone growth regulator significantly reduced the stature of excessively tall sweet corn hybrids, but that ear quality was affected in a negative fashion when applications were made to certain hybrids at any time after late-whorl. Tests in 1989, which included 20 sh-2, se, and su genotypes, showed that 80 percent of the hybrids were similarly affected (cob grew beyond the husk tip). The effect was apparent, however, for high dosage (0.38 lb AI/acre) applications to plants in the late-whorl stage. In further tests, 5 hybrids were treated with Cerone (0.38 lb AI/acre) when the embryonic tassel was 3 in. long. Compared to untreated, the treatment resulted in 27.8 percent reduction in plant height (range 22-32 percent); after the passage of 'Hurricane Hugo', treated plants were 0 percent lodged, compared to 26.6 percent (range 18.6-39.4 percent) lodged in untreated. Trials with Cerone have demonstrated that this chemical is
effective in significantly reducing the stature of excessively tall hybrids, and that treated plants, being shorter, have a much lower propensity to lodge than do untreated. Usage instructions, however, will have to be quite specific as to application rate and timing, lest detrimental ear effects occur.
Impacts
(N/A)
Publications
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Progress 01/01/88 to 12/30/88
Outputs
The effects of Cerone plant growth regulator applied at two dosages to the sweetcorn hybrids Jubilee, Silver Queen, Crisp n' Sweet (sh-2), and Tendertreat (se) at two growth stages were evaluated. Measurements were taken on plant ht., ear ht., ear lth., ear wt., and percent marketable ears. Cerone treatments at both growth stages reduced plant ht. significantly, but all other variables except marketable ears were not affected. Cerone at 0.38 lb AI per acre applied at the early green tassel stage caused marked abnormalities to Jubilee and Crisp n' Sweet, as the cob grew beyond the husk tip producing a significant number of unmarketable ears. Should Cerone become registered for use on sweet corn, results have shown that it is an effective tool to shorten hybrids that are excessively tall, but the parameters of dosage and timing may vary among hybrids.
Impacts
(N/A)
Publications
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Progress 01/01/87 to 12/30/87
Outputs
The effects of 'Cerone' plant growth regulator applied to 'Silver Queen' sweet corn at three growth stages were evaluated. Measurements were taken on plant height, ear height, and fresh market yield. 'Cerone' treatments at all growth stages reduced plant height significantly, but ear height only moderately. Differences in yield were not significant. Given the objective of reducing the stature of 'Silver Queen' to that of standard varieties, the optimum treatment was a single application at 0.25 lb AI/acre, applied at three inches embryonic tassel. The use of 'Cerone' appears to be a viable cultural practice for producers desiring to alter some sweet corn growth characteristics.
Impacts
(N/A)
Publications
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Progress 01/01/86 to 12/30/86
Outputs
Maize dwarf mosaic virus (MDMV) incidence was moderate on late-planted susceptible sweet corns in the Hudson Valley region. Large plots (2 acres) were utilized to compare yields of a susceptible cv. "Bellringer" and an MDMV resistant hybrid HXP 234OY. At harvest maturity, ears were visually rated for percent harvestable ears (salability), and computed to boxes per acre (60 ears per box) based on 30-in. row widths. The resistant hybrid yielded 23 boxes per acre more than the susceptible cv. Under these moderate MDMV infection levels, producers could have realized a potential increase of 138 dollars per acre (at 6 dollars per box). Under severe infection levels, greater economic benefits should result.
Impacts
(N/A)
Publications
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Progress 01/01/85 to 12/30/85
Outputs
Two methods of extraction and estimation of sugars in sweet corn kernels were compared on freeze-dried samples from 2 field experiments. A large volume/sample (1000x) extract with colorimetric estimation of total sugars was more dependable than a low volume/sample (10x) in which individual sugars fructose, glucose and sucrose were estimated by HPLC using refractive index detection. A more sensitive detector would permit large volume/sample extraction and should improve the latter method for genetic and physiological studies of sugars during maturation of sweet corn kernels. Shading of sweet corn at 7 stages of growth and kernel development (66% Shade for 5-7 day periods) had no effect on total or levels of individual sugars. The high sugar levels in the hybrid cultivar 'Silverqueen' were found to be conditioned by a gene(s) which had a dosage effect in the 3N endosperm of reciprocal crosses and backcrosses with 'Commander'. Three super sweet hybrids "Summer
Sweet', 'Miracle', and 'Florida 'Staysweet', were found to have significantly lower leaf feeding damage by European Corn Borer than a normal hybrid, 'Sundance". The super sweets also had lower infestation of ears by ECB than the normal hybrid. These results are contrary to the hypothesis that super sweets would sustain greater damage.
Impacts
(N/A)
Publications
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Progress 01/01/84 to 12/30/84
Outputs
Environmental Effects: In 1983 shade cloth (72% shade) covering plants duringfinal 1/4 of fresh kernel development (19-24 days after silk) reduced % dry wt. (apparently less mature) compared to controls and earlier shade treatments. The lower D.W. was due to lower sugars (28%) with a resultant higher proportion of water soluble starch (phytoglycogen) which makes these kernels appear more mature than the control. In 1984 season replicated shade experiment (66% shade) with 5-7 day treatments during seedling growth, ear differentiation and kernel development stages. Ears were harvested at equal stages of kernel development. No effects on ear or kernel size. Seedling treatment delayed silking and rate of kernel maturation. Treatments applied during second and fourth 1/4's kernel developed reduced & D.W. compared to control. Sugars are presently being determined. Pest Resistance: Thirty-seven commercial corn entries were evaluated for Fall Army Worm reistance using
field infestations and larvae confinement with leaf cages. Only 3 entries showed less than 10% leaf feeding and only one had low reading for both leaf and ear damage. Promising entries will be further evaluated in field and lab studies.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
Quality evaluation: A new microextraction method using 50% Acetonitrile was used to extract sugars from freeze dried edible kernel samples or dry seeds (either bulk or single kernel samples). After microfiltration, the sugars were estimated by HPLC using peak heights. Recovery of sugars in spiked samples was 90-100% and values for individual sugars and total sugars were close to values determined by other methods. Pest resistance: 13 hybrids and genotypes were evaluated in Ulster Co, NY, for maize dwarf mosaic virus resistance. Performance for % marketable ears and yield showed 5 entries have significant resistance to MDMV. Additions of potassium to corn had no apparent effect on MDMV symptom expression, days to silk, or plant height.
Impacts
(N/A)
Publications
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Progress 01/01/82 to 12/30/82
Outputs
Pests: Maize Dwarf Mosaic Virus (MDMV) infection of 22 hybrids in the Hudson Valley was low and there were no significant correlations between infection and % harvestable ears or leaf symptoms. Highest % marketable ears (66%) was on 2 hybrids bred for MDMV resistance. In another trial with heavy natural infestation a hybrid selected for MDMV tolerance had high (5.9 T/A) processing yield. Foliar feeding Fe, Zn, and Mg did not affect MDMV effects on yield. Quality: Canned intact kernel corn has color problems of whole kernel and at base of kernel (black layer). There appears to be a genetic source for freedom from latter problem; the former is probably due to higher sugar in intact kernels. Silverqueen has higher fructose and sucrose than most hybrids and could be another source of genes for high quality sweet corn.
Impacts
(N/A)
Publications
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Progress 01/01/81 to 12/30/81
Outputs
Sensory comparisons of sweet corn hybrids differing in endosperm genotype shouldbe made at comparable maturity. For fresh market evaluation this would be at 22 to 24 standard days after pollination. A standard day (SDAP) of 21 C with a base of 0 C has been proposed. At 24 SDAP most su hybrids have a kernel dry weight (DW) of 23 to 25%. The sh-2 types have a lower % DW and low rate of increase in DW and much higher sugar content but have normal pericarp development and higher insoluble starch than su types. Twice-weekly sprays of fenvalerate and acephate to reduce MDMV transmission by aphids increased marketable ear % by 70.4 and 73.4%, respectively, but had no significant effect on symptom expression; neither treatment resulted in a market quality crop. RXP258, a tolerant hybrid, produced a high quality crop under high disease incidence. Four other tolerant hybrids yielded significantly more than 3 susceptible hybrids, indicating that MDMV tolerance is a realistic
goal.
Impacts
(N/A)
Publications
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Progress 01/01/80 to 12/30/80
Outputs
Pests: Twice-weekly stylet oil sprais reduced MDM (Maize Dwarf Mozaic) infection and increased yield in a June 17 planting. Oil sprays did not reduce infection or increase yield in plantings after June 17. MDM infection reduced ear size and % marketable ears and increased % barren plants. Quality: Intact kernels of several hybrids had higher total sugar, Ca, Mg, Fe and Zn and lower WSP than cut kernels of the same maturity. Canned intact kernels were darker but equal in flavor and texure to cut kernels. Frozen intact kernels were preferred -- flavor and texture -- over cut kernels. Development: Time of kernel development (silk to harvest, 72% moisture) in terms of standard 70 degrees F at 4 base temps was detm. for 4 hybrids at 10 P.D. over 3 years. Base temps. of 40 and 45 gave lower variation than 35 or 50. Rate of development (days) proportional to ear size.
Impacts
(N/A)
Publications
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Progress 01/01/79 to 12/30/79
Outputs
Pests: Reduced yield of sweet corn in Maize Dwarf Mosaic Virus infected plots was due to increased incidence of barren plants. A heredity study of the Zapalote Chico silk resistance factor was ruined by Hurricane David. Susceptibility to corn ear worm increased with increasing nitrogen fertility. Environment: Data on rates of ear development and kernel maturation of 4 hybrids at 10 planting dates over 3 years are being summarized to evaluate effects of heritable and weather factors. Ear size was found to account for 70% of the heritable factors, while temperature was the most important weather variable. Better evaluation of all factors will permit prediction of harvest dates at optimum maturity. Quality: Arnold's centrifuge test, a method which is related to carbohydrate composition of the kernels, was found to be too variable to give reliable estimates of maturity of normal sweet corn hybrids. Hand refractometer readings of soluble solids in the kernels were much
less variable and were highly correlated with kernel moisture. Removal of intact kernels resulted in 15-20% yield increase over cut corn. Kernel removal force was reduced by field application of ethephon but genetic factors are more important.
Impacts
(N/A)
Publications
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